# Connecting ANITA Anomalous Events to a Non-thermal Dark Matter Scenario

## TL;DR

This paper proposes a non-thermal dark matter scenario involving a Z2 odd sector to explain ANITA's anomalous upward-going events, suggesting a hybrid thermal and non-thermal dark matter relic abundance.

## Contribution

It introduces a novel Z2 odd sector model where NLSP decay produces tau leptons, linking dark matter properties to ANITA's observed anomalies.

## Key findings

- Hybrid dark matter scenario explains ANITA events.
- Purely non-thermal dark matter cannot account for event rates.
- Long-lived NLSP decays produce tau leptons passing through Earth.

## Abstract

The ANtarctic Impulsive Transient Antenna (ANITA) collaboration has observed two EeV-energy, upward going events originating from below the horizon. As no standard model (SM) particles, propagating through the earth at such energy and exit angles, can give rise to the required survival probability for the observed events, several beyond standard model (BSM) proposals have come up. We propose a scenario where a $Z_2$ odd sector is responsible for such anomalous events. The next to lightest $Z_2$ odd particle or the next to lightest stable particle (NLSP), created from ultra high energy neutrino interactions with nucleons, can pass through the earth and then decay into the lightest $Z_2$ odd particle or the lightest stable particle (LSP) and a tau lepton. The long-lived nature of the NLSP requires its coupling with the LSP to be very small, keeping the LSP out of thermal equilibrium in the early universe. The LSP can then be a non-thermal dark matter while the tau leptons produced from NLSP decay after passing through the earth can explain the ANITA events. We first show that a purely non-thermal dark matter scenario can not give rise to the required event rates while a hybrid scenario where dark matter can have both thermal as a well non-thermal contribution to its relic abundance, serves the purpose.